Systems and method for delivering reliable datagram service through connection-oriented service

ABSTRACT

A system and method for reliabe delivery of datagram protocol data unit (PDU) packets generated by a network oriented application at a first computing network element to a second computing network element across a network. The method steps include: at the first computing network element, capturing generated datagram packets destined for the second computing network element; determining a size of a payload associated with the datagram and communicating the size of the payload to the second computing element via a reliable connection-oriented transport service PDU; communicating the actual payload to the second computing element via the reliable connection-oriented transport service PDU; and, at the second computing network element, utilizing payload size and payload to reconstruct a datagram PDU including the payload for a network application at the second computing network element. By this technique, reliable datagram PDU transport over the network is ensured.

FIELD OF THE INVENTION

[0001] The present invention relates generally to packet communicationsacross networks, and particularly, to an improved connection-orientedcommunications system for providing reliable datagram packet-basedcommunications.

BACKGROUND OF THE INVENTION

[0002] Currently, a datagram-based communications protocol known as theSimple Network Management Protocol (“SNMP”), is implemented to perform,network management of vendor telecommunications equipment over longdistances across local area networks (LANs) and wide area networks(WANs). For example, in the system 10 as shown in FIG. 1, many vendors12 of a telecommunications carrier 15 (e.g., MCIWorldcom, assignee ofthe present invention) rely on SNMP communications to manage theirequipment across a LAN/WAN 20. Thus, a piece of equipment 13 maygenerate a message about its operational state and this message may becommunicated via SNMP from the equipment to MCIWorldcom's networkmanagement software 16 across the network. In another exampleimplementation, a network operation, administrator or maintenancecenter, e.g., located in North Carolina, may be required to provisionswitches remotely located across the country, e.g., in Texas, via a WAN.

[0003] It is the case that the Simple Network Management Protocol is anunreliable protocol, based on the Internet Protocol Suite's UniformDatagram Packet (“UDP”) protocol. An unreliable protocol is one thatdoes not guarantee delivery of information to its network destination,and thus requires retransmission of datagrams with error managementbeing pushed up into the application layer. Thus, in the above-describedexample, datagrams traveling between North Carolina and Texas via SNMPmay be routine dropped in the WAN 20, possibly causing provisioningactivity to fail. Obviously, the loss of provisioning packet informationfor these switches may be detrimental to the carrier's business.

[0004] When a network is in trouble, e.g., when a large percentage (80%or more) of all network communications are failing, it is very difficultto actually communicate with a device. Even if SNMP were TCP based, itwould be very difficult to communicate with a device under theseconditions. This is because TCP requires a number of contiguous packetsto be sent and received to open a TCP session, and if many of thepackets are lost, TCP would fail. However, with UDP PDUs, no setuppackets are required, and advantageously, single SNMP commands can fitwithin a single datagram. So, if a network is in trouble, datagrams canbe machine gunned at a host, and even if 90% of all packets are beinglost, eventually, the SNMP command will be delivered to the device.Network management is needed most when the network is in trouble, andthis is why the datagram-based SNMP protocol is used.

[0005] Furthermore, the problem with SNMP being an unreliable protocolis that it does not support the notion of a transaction well. Atransaction is a sequence of datagrams being exchanged between a managerand agent to accomplish a task. The SNMP works fine when a managementtask requires only one or two datagrams. However, if a management taskrequires a complex set of datagrams being exchanged, then an unreliableprotocol does not work well, because any datagram element within thetransaction can be lost in the network. A real life example of thisproblem is provisioning data services for telecommunications carriercustomers were setting up high speed data services requires complex SNMPbased transactions.

[0006] No mechanism or technique is currently available to remedy theseproblems. Consequently, it would be highly desirable to implement amechanism that would virtually eliminate the loss of datagram packetstransmitted over a LAN/WAN.

SUMMARY OF THE INVENTION

[0007] The present invent-ion satisfies the above mentioned need byproviding a reliable connection-oriented communications to/from amanagement system and vendor equipment, which have datagram basedcommunications.

[0008] Particularly, the method and system for delivering reliabledatagram service comprises the following components: a device forcapturing datagrams intended to traverse the LAN/WAN; a device forextracting datagram payloads from captured datagrams, with the payloadsbeing typically application level PDUs; a device for sending datagrampayloads through LAN/WAN, by use of a reliable connection-orientedprotocol, e.g., TCP/IP; and, after payload has been sent across LAN/WA,a device for reconstructing the payload as a datagram and sending thereconstructed datagram to the intended local recipient.

[0009] Preferably, this technology may be implemented at the OS level inthe kernel, or it may be implemented as an application level process. Asthe mechanism of the invention allows for non-intrusive hardening ofexisting datagram based communications, existing communications softwaredoes not have to be recompiled to use this technology, thus facilitatingaddition of this technology to existing systems.

[0010] Advantageously, this technology makes datagram communicationsreliable; therefore, it can benefit many different commercialapplications.

BRIEF DESCRIPTION OF THE FIGURES

[0011] The foregoing and other features and advantages of the inventionwill be apparent from the following, more particular description of apreferred embodiment of the invention, as illustrated in theaccompanying drawings. In the drawings, like reference numbers indicateidentical or functionally similar elements.

[0012]FIG. 1 illustrates a typical communications system providingdatagram packet communications over a LAN/WAN between a vendor and anetwork manager;

[0013]FIG. 2 a high level block diagram of the application levelimplementation for providing reliable datagram service according to theinvention;

[0014]FIG. 3 is a detailed illustration of the mechanism 200 forproviding reliable datagram service through a connection-orientedservice according to the preferred embodiment of the invention;

[0015]FIG. 4 illustrates an application level process for reliablydelivering datagrams through a connection-oriented service;

[0016]FIG. 5 illustrates the Tcp2Udp initialization process;

[0017]FIG. 6 is a flow chart depicting the child process for performingthe actual work of moving datagram payloads through the LAN/WAN; and,

[0018]FIG. 7 depicts the functionality of the present invention added toan operating system the form of a device driver.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019]FIG. 2 depicts a high level block diagram of the application levelimplementation or providing reliable datagram service according to theinvention. It is understood that the present invention may beimplemented at the operating system kernel level, as well. As shown inFIG. 2, conceptually there is an application process 40, and anapplication level process 60 for handling datagrams destined for LAN/WANvia TCP/IP, X.25, or any other transport protocol 80, for example. Withan application process implementation, an application's peer host IPaddress is to be changed to the local host's IP address on permit the“application level process” that handles datagrams to catch datagramsheaded for the LAN/WAN, as will be described in greater detail herein.

[0020]FIG. 3 is a detailed illustration of the mechanism 200 forproviding reliable datagram service through a connection-orientedservice according to the preferred embodiment of the invention. As shownin FIG. 3 there is provided a device 230, e.g., an SNM ProvisioningServer (PS) device which includes a network oriented applicationsoftware 240 for generating application level datagram protocol datagramunits (“PDU”) packets. The generated PDU datagram packets are input to areliable datagram service mechanism 250 a which functions to strip thepayload out of each datagram PDU. As an example described herein, suchpayload may comprise switch provisioning data information. The reliabledatagram service mechanism 250 a then communicates the size of thepayload to be sent to a peer computing element 235 setup as a serverprocess, which may comprise a switch device 235, e.g., an AscendFrame/ATM switch platform (proprietary to Lucent Technology Inc.), whichcontains the network oriented application 245, via the LAN/WAN 20. Forthe given example described herein, the network oriented application 245may include software for provisioning the network switches. It isunderstood however, that any application receiving a PDU datagrampayload may be provided. Subsequently, the actual payload (applicationlevel PDU) is sent to the provisioning server or peer computing element235. Specifically, as further shown in FIG. 3, a counterpart reliabledatagram service mechanism 250 b provided at the server 235, receivesthe payload size and the actual payload communicated. Then, thecounterpart reliable datagram service mechanism 250 b reconstructs thedatagram and sends the reconstructed datagram to the local networkoriented application 245, for which the information was targeted.

[0021] The application level process described above for reliabledelivering datagrams through a connection-oriented service is nowdescribed by way of example, as shown in FIG. 4. In this example, UDPPDU payloads are delivered over LAN/WAN 20 using the more reliableTCP/IP transport protocol, however, it is understood that any reliabletransport level protocol may be implemented. As shown in FIG. 4, twoprocesses: “udp2tcp” 255 a and “tcp2udp” 255 b correspond to MDRDSprocess 250 a, 250 b, respectively, as described above, with the tcp2udp255 b executable running on the server device 235, e.g., the Frame/ATMswitch platform, and, the udo2tcp 255 a executable running on the clientdevice 230, e.g., the SNM Provisioning Server (PS) device.

[0022] On the client device 230, the SNM provisioning client isconfigured to talk to the locally implemented udp2tcp program enablingthe client to believe that the udp2tcp program 255 a is the switchdevice 235. Thus, when the client device communicates, it sends its UDPPDUs to the udp2tcp process 255 a. The Udp2tcp process 255 a, takes thepayload data from UDP and sends it to the provisioning networkapplication, e.g., over TCP, to the server process 235 where it isreceived by the tcp2udp executable 255 b. As mentioned by way of exampleherein, the contents of the UDP packet, i.e., the payload information,is another PDU encapsulated by the UDP envelope. This may be a SKIMP PDUor possibly a PDU proprietary to the client.

[0023] The tcp2udp 255 b executable implemented in the server receivesthe UDP payload data and resends the information as a UDP PDU to theswitch device 235. Thus, the switch platform 235 believes the localtcp2udp executable 255 b is the remote network management (SNM) client.

[0024] The “udp2tcp” 255 a and “tcp2udp” 255 b processes are nowdescribed herein with greater particularity.

[0025] As described, the tcp2udp application process lives on theswitch's platform, and is setup as a server process which process isinvoked with the following parameters: a) a TCP Port Number for the TCPport that is used for communications over the LAN/WIN between udp2tcpand tcp2udp; b) a UDP Port Number for the UDP port which is the numberused by the network-oriented application; and, c) an IP Address which isthe IP address of the host running the network-oriented application.This typically will be the local host's address.

[0026]FIG. 5 illustrates the Tcp2Udp initialization process 100. Skilledartisans would be able to devise a similar initialization process forthe Udp2Tcp executable in FIG. 5, as indicated at a first step 103 aTCP/IP socket is opened, using a predefined TCP port number, so that anyclient on any host may connect to the process via LAN/WANcommunications. This port is made ready to except connection requestsmade by udp2tcp processes located on peer hosts. At step 105, callreceipt process threads are initialized for accepting connectionrequests from Udp2tcp processes. These process threads include: 1) aprocess that listens for client process connections (“t_listen”), and,2) a process for accepting, calls from the client process (“t_accept”).The next few steps are implemented to prepare for the receipt ofdatagrams from applications running on the client machine. Specifically,as indicated at step 107, a UDP socket is initialized using thenetwork-oriented application's part number as follows: it opens a UDPendpoint; initializes the socket with address of the server to senddatagrams; and it initializes a UDP unit data structure forsending/receiving information via UDP. Thus, a socket (softwareconnection) is opened to enable reading and writing of UDP datagramwithin the server device.

[0027] After initialization is completed, the process goes into a loop,as indicated at steps 101-115, to wait for connection requests fromudp2tcp, located on remote peer hosts. Particularly, as indicated atstep 110, the process waits for receipt of a connection request fromUdp2tcp using t_listen. A received call from the client process isaccepted using t_accept function, as indicated at step 112. Next, asindicated at step 115, the tcp2udp process clones itself to generate achild tcp2udp process, so there are now two tcp2udp processes: theoriginal process, the parent, which returns to the top of the loop tolisten for more connections, and the clone (child) process, which entersa main loop 119 for sending and receiving message datagrams. It isunderstood that the child process is created utilizing the UNIXapplication utility fork( ), for example, having the opened socket (step103) for processing the received PDUs. After spawning the child process,described herein with respect to FIG. 6, the process then returns tostep 110 so the parent may wait for further connection requests from aclient process.

[0028] Specifically, the child tcp2udp process main processing loop 119performs the actual work of moving datagram payloads through the LAN/WANas now described in greater detail in view of FIG. 6. In the preferredembodiment, a multiplexed I/O scheme is implemented, whereby the loopwatches for data to be read from either the TCP socket or from the UDPsocket. Data available on the UDP socket are outgoing UDP datagramstraveling from an application on the local host across the LAN/WAN.Information available on the TCP socket is incoming application levelPDUs, which have traveled across the LAN/WAN and are destined for anapplication on the local host.

[0029] Particularly, the Tcp2udp process is configured as a serverprocess and may support multiple concurrent connections. That is, in thepreferred embodiment, communications between the udp2tcp and tcp2udpprocesses is two way asynchronous multiplexed I/O, based on Select( ) (aUNIX application utility). Thus, as shown in FIG. 6, at step 120, adecision is first made as to whether the current data received is datafrom the udp2tcp process across the LAN/WAN via TCP, or, is data fromthe server application itself. If the data available is received fromthe udp2tcp process, then at step 130 the size of the PDU that isexpected to be transmitted across the LAN/WAN via TCP (from the udp2tcpprocess) is read. Then, at step 135, the actual PDU data received viathe TCP connection is read, and, at step 140, an application level UDPPDU packet is formed that comprises data read from the TCP/IP. Skilledartisans may easily generate the UDP PDU packets from the parameterinformation and from techniques described in the reference W. RichardStevens, “UNIX Network Programming”, Prentice-Hall, Inc., 1990 (ISBN0-12-949876-1), the whole contents and disclosure of which isincorporated by reference as if fully set forth herein. Finally, at step145, the new application level UDP datagram is sent to thenetwork-oriented application using the UDP socket. The process thenproceeds back to step 120 for the next I/O select. It is understood thatwhen the local server application receives the datagram, it will believeit has received information directly from its peer computing entity. Itis unaware that udp2tcp and tcp2udp handled the information.

[0030] If, at step 120, data is received from the server application,i.e., information is available on the UDP socket, then, the processproceeds to step 150, where the UDP PDU (datagram) received from theLocal network-oriented server application is read into tcp2udp. Then, atstep 155, the size of the PDU data (payload) received via the UDP isobtained, and, at step 160, the PDU data size is sent to the udp2Tcpprocess via the TCP connection. This allows the receiver (e.g., client)to know in advance the size of the information to be transmitted overTCP. It is understood that the size of the PDU must be successfully sentbefore the actual PDU can be transmitted because TCP is a reliable,stream oriented protocol. Finally, at step 165, the actual payload (PDUdata) is sent to the udp2Tcp process via TCP/IP.

[0031] According to the invention, the Udp2Tcp process is virtuallyidentical to the Tcp2Udp process describes herein. That is, both Udp2Tcpand Tcp2Udp processes mirror each other as both are equipped to receiveand send datagram packets via a connection-oriented protocol, e.g.,TCP/IP, once a virtual connection over a network is established. Thus,the UDP2TCP application process lives on the network managementplatform, and is setup as a server process which process is invoked withthe following parameters: a) a TCP Port Number for the TCP port that isused for communications over fine LAN/WAN between udp2tcp and tcp2udp;b) a UDP Port Number for the UDP port which is the number used by thenetwork-oriented application; and, c) an IP Address which is the IPaddress of the host running the network-oriented application. TheUdp2Tcp initialization process is similar to the above-describedinitialization process relating to the Tcp2Udp executable. That is,udp2tcp first opens a TCP socket, using the LAN/WAN communications portwhich port is made ready to except connection requests made by tcp2udpprocesses located on peer hosts. Then, using the network-orientedapplication's port number a UDP socket is initialized. To do this, a UDPendpoint (socket) is opened and the endpoint is conditioned to receivediagram messages from any host. Then, a TCP socket is initialized withthe remote host address and network-oriented application port number. Aconnection request is then sent over the LAN/WAN to the remote host. Atthis point, on the other side of the LAN/WAN the udp2tcp process acceptshe connection, creates a clone process, and the clone process waits toprocess incoming and going messages.

[0032] Thus, after udp2tcp initialization is completed, the processenters a main loop for processing incoming and outgoing messages. Thisloop is exactly the same as the main loop used by tcp2udp as describedherein with respect to FIG. 6. That is, a multiplexed or scheme isimplemented to determine when incoming or outgoing communications areavailable to be processed. Application level PDUs being sent across theLAN/WAN are done with two write operations, as discussed earlier; thefirst write send the size of the PDU and the second write studs theactual PDU.

[0033] As mentioned, the present invention may be implemented at theoperating system (OS) level. FIG. 7 depicts the functionality of thepresent invention added to the OS in the form of a device driver 70which may provide functionality for both TCP/IP, X.25 and other OpenSystems Interface communications/transport protocols. A kernelimplementation is faster than when implemented as an applicationprocess.

[0034] While the invention has been particularly shown and describedwith reference to preferred embodiments thereof, it will be understoodby those skilled in the relevant art that various chances in form anddetails may be made therein without departing from the spirit and scopeof the invention.

What is claimed is:
 1. A method for reliable delivery of datagramprotocol data unit (PDU) packets generated by a network orientedapplication at a first computing network element to a second computingnetwork element across a network, a datagram packet typically comprisinga data payload, said method comprising: (a) at said first computingnetwork element, capturing said generated datagram packets destined forsaid second computing network element; (b) determining a size of saidpayload and communicating size of said payload to said second computingelement via reliable connection-oriented transport service PDU; (c)communicating payload to said second computing element via reliableconnection-oriented transport service PDU; and, (d) at said secondcomputing network element, utilizing payload size and payload toreconstruct a datagram PDU including said payload for a networkapplication at said second computing network element, whereby reliabledatagram PDU transport over said network is ensured.